This invention pertains to an improved suspension and damping system to provide "smooth course" and "soft ride" characteristics to vehicles used in moving passengers and freight along a supporting surface, and more specifically to a trackway guided vehicle traveling at speeds upward from 80 miles an hour.
In the field of flange wheel solid rail train systems used throughout the world, there has been little change in the art for the past 150 years. Although this basic system concept has been highly successful in the past, limitations which become manifested at highest speeds render their use on faster and more comfortable trains impractical and infeasible. Although flanged wheels are entirely successful the relatively slow speeds of the nineteenth and the first half of the 20th century, presently required higher speeds, have interposed limitations on this mode of travel since, at such speeds, the skip oscillations or jumping of the wheels along the track occurs which results in a rough and uncomfortable ride. The high speed limitations have not successfully been overcome by currently designed vehicles using prior art suspension systems.
Any form of the present wheeled land transport, which whatever its design, has to run over a roadbed which has a more or less irregular surface. At the present time, all the railways in the world, almost without exception, use vehicles with passive suspension systems. At slow speeds these systems perform the task of providing a soft ride relatively well but are nearly totally unsuccessful as high speeds are reached.
It has been recently realized that the only way to successfully provide ease of ride conditions for the passengers and freight through a range of various speeds of a railway vehicle is to be able to change the vehicle's suspension properties while it is in motion to satisfy varying physical conditions. In the October 1970 issue of "Automotive News" a new suspension system to be utilized in a tracked air cushion vehicle is described. The system uses three layers of suspension separating the passenger compartment from the guideway. The first chassis layer consists of jet air cushions. Second intermediate and third body layers consist of passive air springs for suspension and active conventional hydraulic elements for damping. Accelerometers on both chassis and body layers are provided to generate signals when either move from a predetermined position. These signals are fed into an onboard computer to calculate the hydraulic pressure required by the various hydraulic elements to maintain the body on a smooth path.
Various luxury automobiles use similar passive springs for suspension and active hydraulic or pneumatic/hydraulic damping means working in combination therewith as well as hydraulic or hydraulic/pneumatic means for both suspension and active damping.
M. W. Dewey, U.S. Pat. No. 408,465, and J. S Rogers, U.S. Pat. No. 833,635, disclose electromagnetic attractive supports to provide friction reduction between sprung and unsprung parts of a railway running gear or truck system. Dewey provides an electromagnetic type bearing between the axle and weight supporting member at the ends of the axle and Rogers provides an electromagnetic support between the center of the axle and the weight supporting member. Neither of these teachings provided for an absence of physical contact between the truck assemblies and the weight supporting member, therefore, neither teach prevention of track vibration transmission to the weight supporting member nor an active control of the electromagnetic force field that could provide and maintain an air gap between the truck assembly and the weight support member to prevent this vibration transmission.
The German patents to Herman Kemper, Nos. 643,316 (1937), 644,302 (1938), and 707,032 (1941), disclose the suspension of tracked vehicles by use of electromagnets. The 1938 patent is specifically concerned with providing feedback for preventing oscillations of the suspended vehicle caused by the kinetic energy acquired by the vehicle in response to correction of position and, further, in preventing high acceleration of change of motor energy level from causing further changes in energy level when the correct level is reached. The position feedback voltage produces a directing magnetic force to return the suspended vehicle to the correct location relative to the rails. This type of position feedback voltage is undesirable at high speeds because the sprung portion will try to follow the perturbations of the rail resulting in a rough ride.
The various prior art vehicles having sprung and unsprung portions have common disadvantages, namely, that each has mechanically interconnecting parts that must periodically be replaced due to wear. In addition, the prior art has not disclosed how suspension systems such as disclosed by Kemper, Roger, and Dewey would be combined to provide an active magnetic suspension for a sprung/unsprung system in the manner of the hydraulic/pneumatic suspension system of the referenced automotive new disclosure.